Nontuberculous mycobacteria, which are all mycobacteria except Mycobacterium tuberculosis and Mycobacterium leprae, are known to cover approximately 140 species and are widely found in natural environments, such as soils and water. However, as searches regarding acquired immune deficiency syndrome (AIDS) epidemic from the 1980s reported that the Mycobacterium strains are the main causative bacteria of opportunistic infections of AIDS patients and may cause severe pulmonary diseases as well as infections in normal patients, and the clinical importance thereof is growing.
Recently, the USA and many European countries, which have a low prevalence of tuberculosis, have seen an increase in the incidence of infections caused by nontuberculous mycobacteria. Also in Korea, infections by nontuberculous mycobacteria have increased although the incidence of tuberculosis has been reduced. In addition, tuberculosis is still one of the most serious health problems globally, and the incidence of tuberculosis in Korean is very high with 78.9 cases per 100,000 people in 2011.
Owing to a policy that granted medical insurance for the performing of liquid culture of tuberculosis bacteria in 2009 in Korea, there was an increase in the number of laboratories designed to perform liquid culture. The liquid culture detects nontuberculous mycobacteria more often than does the solid culture of the conventional art. According to recent reports, nontuberculous mycobacteria were isolated in about 12% of smear/culture-positive Mycobacterium tuberculosis cases, and nontuberculous mycobacteria isolated from the sputum account for about 10-20% of pulmonary disease cases in Japan, Hong Kong, and Korea, and about 40-50% of pulmonary disease in the USA, Canada, and West Europe. In particular, it has been reported that mycobacteria isolated from clinical specimens, containing nontuberculous mycobacteria, accounted for about 33% of cases in 1979-1980 and about 75% of cases in 1992 in the USA.
Most of all, the pulmonary disease by nontuberculous mycobacteria is prone to be misdiagnosed due to the likeness to slowly advanced pulmonary disease. However, drugs that are sensitive to Mycobacterium tuberculosis and nontuberculous mycobacteria are different, and therefore, there is a growing demand for developing a prompt and accurate selective detection method of Mycobacterium tuberculosis and nontuberculous mycobacteria.
However, the currently marketable test reagents used to detect Mycobacterium tuberculosis and nontuberculous mycobacteria are problematic in view of the accuracy in detection and diagnosis since the test reagents employ nucleotide sequences that are unique to nontuberculous mycobacteria, as well as nucleotide sequences also present in Mycobacterium tuberculosis. As a result, Mycobacterium tuberculosis within a particular concentration range reacts only with nontuberculous mycobacteria detection primer without reacting with Mycobacterium tuberculosis detection primer, so Mycobacterium tuberculosis is wrongly identified as nontuberculous mycobacteria, or only nontuberculous mycobacteria are detected when nontuberculous mycobacteria and Mycobacterium tuberculosis are simultaneously present.
In addition, there are significant differences in the pathophysiological and epidemiological characteristics between Mycobacterium tuberculosis and nontuberculous mycobacteria. For example, Mycobacterium tuberculosis is infectious between persons, but nontuberculous mycobacteria are not infectious between persons. Therefore, Mycobacterium tuberculosis needs to be detected selectively from nontuberculous mycobacteria. In addition, since respective species of nontuberculous mycobacteria have a great variety of pathogenicity, the nontuberculous mycobacteria need to be specifically identified to select appropriate therapeutic medicines. In addition, the conventional mycobacteria culture and identification tests have the disadvantage of taking 2-4 weeks.
Accordingly, prompt and accurate selective detection methods of Mycobacterium tuberculosis and nontuberculous mycobacteria using a primer set and/or probe, capable of recognizing unique nucleotide sequences present in nontuberculous mycobacteria but not Mycobacterium tuberculosis, are urgently required.
Throughout the entire specification, many papers and patent documents are referenced and their citations are represented. The disclosure of cited papers and patent documents are entirely incorporated by reference into the present specification, and the level of the technical field within which the present invention falls, and details of the present invention are explained more clearly.